Here’s a great resource on Moodle.org that has everything you need to know (want to know?) about Blogs in Moodle 2.0 (including a great video). Enjoy.
Blogs in Moodle are user based – each user has their own Blog. Admins, teachers, and students can create Tags – Admins can create site level tags, teachers can create Course level tags, and students can create their own list of tags.
When a blog entry is created, a user can select which tags they wish to associate with their new entry. Multiple tags can be selected. Users can also select who they want the blog entry to be available to (depending on the blog visibility site setting).
Read more at http://docs.moodle.org/20/en/Blogs